The majority of gasoline sold at retail is through self service dispensers located on islands adjacent a building housing the attendant cashier. Necessarily, the dispensers, and the flexible hoses attach thereto, must be located adjacent vehicle lanes whereby the vehicle maybe located adjacent the dispenser during refueling.
Because of the close proximity of the dispenser to the vehicle lanes it is common for accidents to occur wherein a vehicle entering or leaving a lane accidentally strikes a dispenser. To minimize such accidents it is common to mount the dispensers upon raised concrete islands and inbed concrete and steel barriers in the islands adjacent the dispensers. However, while such protective barriers are effective in many instances, it is necessary to provide access to the dispensers, and the degree to which the dispenser can be protected is limited, and dispensers are often involved in accidents. Vehicles crossing the vehicle lane may strike a dispenser from the side, and thousands of accidents occur each year in the United States wherein a gasoline dispenser is struck by a vehicle and life threatening and property damaging fires often result.
While gasoline dispensers often utilize frangible fluid conduit connections to terminate gasoline flow in the event of dispenser impact or excessive tension on the outlet hose such conduit safety devices are not dependable as they will often corrode and become inoperative, and heretofore a dependable electrical safety system for gasoline dispenser systems and other hazardous fuel dispensing systems has not been available.
It is an object of the invention to provide a safety system for hazardous fuel dispenser systems such as occur in gasoline service stations wherein electrical impact sensing switches are associated with each dispenser to immediately sense dispenser movement and deactivate the supply of gasoline to the dispenser to minimize hazardous fluid loss.
Another object of the invention is to provide a hazardous fluid dispenser safety system employing electric supply pumps and dispensers wherein electrical impact sensing switches located at each dispenser are electrically connected to a central electrical supply system for a plurality of pumps wherein the entire pumping control circuit is deenergized upon dispenser impact occurring.
An additional object of the invention is to provide a hazardous fluid safety dispenser safety system utilizing an electrical impact safety sensing switch which may be readily mounted upon the conventional electrical circuit components used with gasoline dispensers.
A further object of the invention is to provide an electric impact sensing switch for use with hazardous fluid dispenser safety systems wherein liquid mercury is retained within a closed envelope selectively associating with electrical terminals whereby impact forces imposed upon a dispenser housing on which the switch is mounted will cause movement of the mercury to close the circuit between the contacts and the switch envelope is protected from impact and exterior forces. In the practice of the invention an impact sensing switch utilizing liquid mercury encapsulated within a protective environment is mounted upon a conventional electric circuit box within each dispenser of a gasoline service station, for instance. The terminals of the impact sensing switch are connected to a control unit associated with the emergency power cut off switch of the electrical power circuit supplying the pumps which provide gasoline to the dispensers. Preferably, this circuitry also controls all electricity to the lights and other electrical devices in the vicinity of the dispensing area.
Upon the circuit of any impact sensing switch closing the primary emergency cut off switch is activated to deenergize the gasoline supplying pumps and other circuits to the dispensing area, and the potential fire hazard is immediately controlled and minimized. The safety system of the invention can only be rearmed and reset by authorized personnel, and the system cannot be inadvertently deactivated by unauthorized personnel.